Research on suction capacity and dust suppression performance of a reverse circulation air hammer in tunnel drilling

The presence of respirable dust in underground space causes serious health hazards for workers while in tunnel drilling, which could result in pneumoconiosis and silicosis. In order to control the dust dispersion and improve the environment quality of underground space while in tunnel drilling, an innovative drilling system with a reverse circulation (RC) air hammer is proposed. In addition, the structure of the RC air hammer with double-row suction nozzles is specially designed, which contributes to the improvement of suction capacity of the air hammer. Totally four structural parameters of the RC air hammer are optimized, and the effects of four structural parameters on suction capacity of the air hammer also have been investigated by means of Computational Fluid Dynamics (CFD) simulation method, which is crucial for the dust suppression performance of the RC air hammer drilling system. Simulation results have shown that the inclination angle (theta(s)) has the greatest influence on suction capacity among the four structural parameters, which is descendingly followed by the defection angle (theta(d)), the vertical space (L) and the horizontal space (S). Meanwhile, the optimal parameters configuration of the air hammer with double-row suction nozzles has been obtained. Additionally, the laboratory and field tests on the RC drilling system with optimal parameter configuration have been subsequently conducted, and no dust or rock cuttings were suspended in the underground space, which dramatically improves the internal working conditions of tunneling drilling. In conclusion, the suction capacity of the air hammer with optimized structural configuration is outstanding, and the dust suppression performance of the RC air hammer drilling system is excellent, which is applicable to eliminate the dust dispersion in underground tunnel drilling.